1. Field
One embodiment of the present invention relates to a method for manufacturing a substrate for a discrete track recording media and a method for manufacturing a discrete track recording media.
2. Description of the Related Art
In improving track density of a hard disk drive (HDD), the problem of interference with adjacent tracks has become obvious. In particular, a reduction in write-blur due to a fringe effect of a write head magnetic field is an important technical problem. A discrete track recording media (DTR media) in which recording tracks are physically separated can reduce a side-erase phenomenon at the time of writing, and a side-read phenomenon that information of adjacent tracks are mixed up at the time of reading, and the like. Consequently, it is possible to greatly improve the track density, which can provide a magnetic recording media onto which high-density recording is possible.
Methods for manufacturing a DTR media mainly include a method of magnetic film etching type and a method of substrate etching type. The method for manufacturing a DTR media of magnetic film etching type involves a large number of manufacturing steps and is thus expected to increase costs. On the other hand, a method for manufacturing a DTR media of substrate etching type is suitable for mass production; the method first manufactures a substrate having protrusions and recesses and deposits a magnetic layer on the substrate by a sputtering method as is the case with the prior art. However, in a DTR media manufactured in accordance with the method of substrate etching type, the top surfaces of the protrusions are inferior in flatness. It is thus difficult to perform write and read operations using a head with low flying height. If a DTR media is directly manufactured by the method of substrate etching type including an imprinting method, burrs may be created at the edges of the protrusions. This may affect subsequent deposition of a magnetic film to preclude the tops of recording tracks from retaining flatness. If a DTR media is manufactured by the method of substrate etching type, a magnetic material deposited on a remaining resist that has failed to be removed may be peeled off, which degrades a head disk interface (HDI).
Jpn. Pat. Appln. KOKAI Publication No. 2004-79992 discloses a semiconductor manufacturing process in which contaminating particles are removed by a cryogenic cleaning process using CO2 after chemical mechanical polishing (CMP) of a semiconductor material. In this method, liquid CO2 is jet sprayed through a specially designed nozzle, for example, under a pressure of 850 psi (5.8 MPa) at 25° C. The liquid CO2 is jet sprayed in an atmospheric pressure, and thus is rapidly expanded and evaporated into gaseous CO2. Further, with lowering of temperature, part of the gaseous CO2 forms carbon dioxide snow containing solid and liquid CO2. The flow of the gaseous and solid CO2 is directed to the wafer surface using the nozzle. Cryogenic particles that reach the wafer surface at a high speed and collide with contaminating particles can overcome adhesion of the contaminating particles to the wafer surface through transfer of momentum between the cryogenic particles and contaminating particles, and can remove the contaminating particles directly. In Jpn. Pat. Appln. KOKAI Publication No. 2004-79992, however, contaminating particles to be removed are at most 0.3 μm in size. Burrs that may result from the manufacture of a DTR media using a method of substrate etching type are much larger than those to be removed in Jpn. Pat. Appln. KOKAI Publication No. 2004-7992. Further, the burrs to be removed are composed of the same material as that of the substrate. This precludes the burrs from being removed.
U.S. Pat. No. 5,853,962 discloses a method and apparatus for removing photoresist and redeposited materials on a semiconductor using liquid carbon dioxide snow. However, an incomplete result was obtained from an attempt to remove burrs from a substrate after an imprint step using the apparatus described in U.S. Pat. No. 5,853,962. The cause is expected to be similar to that of the disadvantage of Jpn. Pat. Appln. KOKAI Publication No. 2004-79992.